DESCRIPTION: The efficacy and safety of photodynamic therapy (PDT) depends on an understanding of photosensitizer and light biology and dosimetry. Therefore, the ability to accurately determine photosensitizer levels in tumors and at-risk normal tissues is of utmost importance. The goal of this work is to develop and test a prototype system for fluorescence based measurement of photosensitizer uptake in tissue, to improve photodynamic therapy (PDT) dosimetry. The fiber optic system is designed to quantify photosensitizer concentration by detecting a fluorescence intensity signal which minimizes the impact of the tissue optical properties. The bundle is also designed to maximize the signal intensity, allowing quantitation of low concentrations of photosensitizers. Specialized designs have been developed for tissue surface measurement, interstitial measurement and sampling of drawn blood samples. The system is flexible enough to measure either porphyrin-based or phthalocyanine-based photosensitizers, and will specifically be tested in aminolevulinic acid-induced protoporphyrin IX (ALA - PpIX), Photofrin and aluminum disuiphonated phthalocynanine. The system design will be tested in three specific applications where PDT can be successfully commercialized, including (i) veterinary animal tumor therapy, (ii) research in experimental animal tumors, and (iii) adjuvant therapy for human brain tumors after resection. In order to successfully evaluate the system in these different PDT markets, prototype systems will be developed and tested in academic research labs at Dartmouth Medical School and the University of Toronto. The tests will (i) determine how robust the design is, (ii) determine if this dosimetry method improves PDT treatment outcome and (iii) demonstrate safety in human use, prior to commercial development. PROPOSED COMMERCIAL APPLICATION: Not Available